Wednesday, December 31, 2008

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Astronomers Aim to Grasp Mysterious Dark Matter Buzz Up Send Email IM Share Digg Facebook Newsvine del.icio.us Reddit StumbleUpon Technorati Yahoo! Bookmarks Print Clara MoskowitzSpecial to SPACE.comSPACE.com clara Moskowitzspecial To Space.comspace.com – Mon Dec 29, 9:07 am ET AFP/NASA/File – This August 2008 image taken by the Hubble Space Telescope and Chandra X-ray Observatory show a clear … For the past quarter century, dark matter has been a mystery we've just had to live with. But the time may be getting close when science can finally unveil what this befuddling stuff is that makes up most of the matter in the universe.

Dark matter can't be seen. Nobody even knows what it is. But it must be there, because without it galaxies would fly apart.

Upcoming experiments on Earth such as the Large Hadron Collider (LHC) particle accelerator in Switzerland, and a new spacecraft called Gaia set to launch in 2011, could be the key to closing the case on one of the biggest unsolved mysteries in science.

A disturbing truth is accepted by most astronomers: There is a lot more stuff in the universe than what we can see. Scientists now think visible matter — all the planets, stars, and galaxies that shine down on us — represents only about 4 percent of the mass-energy budget of the universe, while dark matter and its even more esoteric cousin, dark energy, make up the rest.

"There is no consensus actually at all as to what dark matter is," said Gerard Gilmore, an astronomer at the University of Cambridge who wrote a recent essay for the Dec. 5 issue of the journal Science about the search for dark matter.

A leading hypothesis posits that dark matter is composed of some kind of exotic particle, yet to be detected, that doesn't interact with light, so we can't see it. One such theorized class of particles is called WIMPs (Weakly interacting massive particles), which are thought to be neutral in charge and weigh more than 100 times the mass of a proton.

Atom smasher

The newly-opened LHC, a 17-mile-long (27 kilometer-long) underground ring in which sprays of protons speed around and crash into each other, could be the first experiment to detect WIMPS. The particle accelerator officially went online in September 2008, but was halted shortly after due to a fault with its construction — it's due to go back online in the summer of 2009. Since the LHC is the largest and most powerful atom smasher ever built, its collisions could produce the extremely high energies needed to create the elusive particles.

In fact, the LHC will likely create a host of never-before-seen particles, opening up a realm of the universe that physicists have been eager to explore.

"The assumption is, there will be whole families of new types of particles," Gilmore said in a podcast interview with a reporter from Science. "The challenge then is to say, well OK, we now then have a new set of ingredients in our recipe for how nature is put together, but what is the recipe that uses this set of ingredients? I.e., what mix of these particles does nature actually use to create the universe, and how?"

Weighing the universe

That's where Gaia comes in. The European Space Agency satellite is designed to measure positions and speeds of about 1 billion nearby stars with unprecedented precision. Its vision is so sharp it should be able to discern the equivalent of a shirt button on the surface of the moon as seen from Earth, Gilmore said.

By establishing where things are in our galaxy, the spacecraft will help scientists measure the weight and distribution of mass in the Milky Way in much greater detail than ever before. These measurements are vital for models that attempt to describe how the pull of dark matter has shaped our galaxy.

"What Gaia will do is measure the distances of stuff and measure how they're moving in three dimensions around space to much better precision than we've had before, which will allow us to weigh things on all sorts of scales down to the smallest scales we can find," Gilmore said. "They will tell us to exquisite precision how the dark matter is distributed in space, which is the recipe we need to determine its properties."

Original Story: Astronomers Aim to Grasp Mysterious Dark Matter SPACE.com offers rich and compelling content about space science, travel and exploration as well as astronomy, technology, business news and more. The site boasts a variety of popular features including our space image of the day and other space pictures,space videos, Top 10s, Trivia, podcasts and Amazing Images submitted by our users. Join our community, sign up for our free newsletters and register for our RSS Feeds today!

Friday, December 26, 2008

A comet, an eclipse, a supernova, an alignment of planets - was the Star of Bethlehem, said to have led the wise men to the Baby Jesus, a real astronomical event?

Some 2,000 years ago, wise men saw an incredible star shining over the Holy Land. It was their signal to embark on an epic journey to visit the new Messiah. But what exactly was the Star of Bethlehem?

Modern science is unravelling the mystery behind one of the most famous astronomical stories in history. New developments in technology allow astronomers to map the ancient night skies with extraordinary accuracy.

As they study the movements of the planets and stars, experts are challenging the traditional assumption that it was a blazing comet - instead there are several unusual astronomical events that the wise men could have seen in the skies.

The Bible tells us remarkably little about the star, with only the Gospel of St Matthew mentioning it. He records the wise men asking: "Where is he who has been born King of the Jews? For we have seen his star in the east and have come to worship him."

No date or detailed description is given. Even the identity of the men is obscure. Rather than the kings of popular imagination, the wise men are thought to have been priests from Persia, known as Magi. Keen astrologers who looked to the stars for guidance, the Magi combined science with faith to predict the birth of a new Messiah.

So what prompted them to travel to Bethlehem? Most experts agree Jesus was born in 4BC or earlier, as King Herod, who ruled over Judea at the time, is recorded as dying in 4BC. Now astronomers have identified four celestial events in this period that could have been the Star of Bethlehem.

TRIPLE CONJUNCTION OF PLANETS

An ancient clay tablet, now in the British Museum, is a key part of one theory which says the star was a rare series of planetary meetings, known as a triple conjunction.

This happened between Jupiter and Saturn and occurred in the night sky in 7BC, says Dr David Hughes, emeritus professor of astronomy at the University of Sheffield.

Jupiter, the royal star, and Saturn came together three times over several months. Significantly, this happened during the constellation of Pisces, a sign associated with Israel.

There is evidence on the clay tablet that Persian astronomers predicted this. The tablet calculates solar, lunar and planetary activity for that year, and describes the conjunctions.

ECLIPSE OF JUPITER

A 2,000-year-old coin, minted north of Judea, is part of the evidence behind another theory. Dr Mike Molnar of Rutgers University, New Jersey, believes the star could have been an occultation, or eclipse, of the moon with Jupiter on 17 April 6BC.

He argues the Magi saw the star in the constellation of Aries, not Pisces. The coin depicts Aries the ram leaping across the sky and looking back at a star.

According to astrological texts from the time, Aries ruled over Judea, with Jerusalem as the capital of the Near East, making it the sign of the Jews.

Dr Molnar believes the Magi saw this eclipse. Just before sunrise, Jupiter would have risen in the east, just as St Matthew describes their sighting of the Star. Then, as the moon passed directly between Earth and Jupiter, the kingmaker planet was hidden from view.

SUPERNOVA

Some think the star could have been a much bigger celestial event. European Space Agency astronomer Dr Mark Kidger believes it would have taken more than unusual planetary movements to persuade such seasoned astronomical experts to travel to Judea.

The Magi could have seen a star entering its supernova phase, one of the most energetic and explosive events known to astronomers.

He has even identified a candidate - DO Aquilae - which erupted in 1927 and is likely to have erupted several times previously. If it had erupted 2,000 years ago, the Magi would have seen it just above the horizon, in the east.

He hopes radio telescopes in the future will be able to detect a faint bubble of expanding gas around Aquilae and calculate when exactly the bubble started to expand.

TWO PLANETS LOOKING LIKE ONE BRIGHT LIGHT

One theory has the most surprising twist. The date for celebrating Christmas was only fixed centuries after the event - and is questioned by many - but Texan law professor and astronomer Rick Larson believes Jesus really could have been born on 25 December. But on 25 December 2BC.

Unlike other astronomers, he has looked at later celestial events because he thinks the calculation of King Herod's death is inaccurate. The 4BC date is based on the writings of the historian Josephus, but every Josephus manuscript he has studied dating before 1544 is consistent with Herod having died in 1BC.

In 2BC Jupiter met up with one of the brightest stars in the sky, Regulus, known by the Magi as the "little king". Nine months later, Jupiter met Venus, known as the mother planet. These meetings would have been symbolically significant, as was the timescale involved.

The planets would have seemed so close they would have looked like one bright light in the sky. Professor Larson believes this light was what prompted the Magi to travel to the east. As they made their way, Jupiter continued to move across the sky until it appeared to stand still over Bethlehem.

Below is a selection of your comments.

Could anyone provide a simple text or explanation for young children? At school we have been looking out for the "Christmas Star" in the early evening and morning skies, but as a non-astronomer I don't really know how to explain it. Catherine Vincer, Taunton, Somerset

Catherine, a lot of planetaria around the country will be running a Christmas Star show at the moment. There's a map of most sites in the UK at planetarium.org.uk. Andy, Newcastle

Surely trying to find a factual explanation for a more than likely fictitious event is impossible. There are just as many interpretations for the story of the birth of Jesus as there are possibilities for notable cosmological events around the same time. Mike Shawcross, London

Back in 2007 The Archbishop of Canterbury said that the Christmas story of the Three Wise Men was nothing but a 'legend'. Even the heads of this religion don't believe a word of it. Nigel Martin, High Wycombe

I think some of you need to brush up on your historical facts before making such bold statements. Anyway, if you take the viewpoint that God is real, which you must do in order to give this idea serious consideration rather than a passing thought, then you have to consider that God is all powerful by definition and can bring about events such as this in a manner that he chooses.

From this viewpoint, He created science and can use it or he can "break the rules" and use supernatural methods ie angels etc. This being said, the reason why the star is not such a big issue and is merely mentioned in Matthew is because he is talking about the coming of the Messiah. At Christmas diner I will not spend much time noticing the sprouts but I will definitely relish the turkey. Dave, High Wycombe

The star of Bethlehem was not any of the astronomical events listed here. It was a metaphor. Light is a common metaphor throughout the Jewish and Christian scriptures, and is almost universal in other religions too. We should not spend time searching for a historical event to explain this star; rather we should be contemplating what it means for a child born 2,000 years to be described as "the light of the world". David Brown, London

Whatever the explanation for the star (and it's a question scientists could argue about for another 2000 years), the point is that this marked the arrival of God on earth in human form. The creator of the stars, planets and everything that exists had arrived in Bethlehem and He wasn't going to let that go unnoticed. Julia, Birmingham

I thought that the more scholarly New Testament experts were generally agreed that the Nativity stories were made up out of whole cloth, so as to make ancient prophecies appear to be fulfilled. Moreover, if a star or planet is spotted in the east, it will be in the west a few hours later (unless it is only visible in the east just before dawn); and if the Magi came from the east, how could they have seen the star in the east and over Bethlehem? Tim Weakley, Dundee

One problem with working out what's meant by the passage in Matthew is the ambiguity of "in the east"; are the Magi in the east, or is the star? Persian Magi would have travelled west to Jerusalem, not east as Prof Larson's theory seems to require. And Aquilae is not (yet) a supernova, but has erupted as a nova (a different sort of event) several times - dating earlier novae is prohibitively difficult, though. Alex Roberts, London, UK

A very appropriate signal from the Almighty, whatever the explanation. Cdr David Aldrich, Exford, Somerset, UK

Interesting, but in the story of Jesus this was no ordinary star - it doesn't stay on high, but moves as a guide and comes to rest very near the infant Jesus (Matthew 2.9-10). In the NRSV translation it says "until it stopped".

This links onto how the ancients and Jews viewed stars. The ancients believed stars to be animate beings and the Jews identified them with angels (look at Job 38.7). The prominent Greek medieval theologian Theophylact and the New Testament Apocryphal book the Arabic Gospel of the Infancy must be right in identifying the star with an angel, and you can compare this with the angelic guide of the Exodus (Ex 23.20,23, 32.34).

The star was about confirming who Jesus was. Of course it depends on what you believe in as to whether you take this view. Ultimately though looking for a scientific explanation misses Matthew's point. Mike Lowe, Burton on Trent

Since the story of the wise men is only mentioned in Matthew's gospel, which itself was not written until several decades after the time of Jesus, probably not even by Matthew, then why consider the story of the wise men to be at all reliable?

A lot more needs to be explained than just the nature of the "star" - how they knew to go to Bethlehem, for instance, when Jerusalem would surely have been the more obvious target, and how they precisely located Jesus within that town.

The most probable explanation is surely that this story is not true and was added later by Christian writers to support their case that Jesus was divine - after all, it wouldn't be the first instance where a story in the Bible has been exaggerated. Peter, London

Another interesting possibility is a metaphysical explanation. When working with the energy system, known as the chakra system, one of the energy centres is known as the Christ centre, and this is felt on the forehead. When meditating on this energy point , a bright star of energy can be perceived and this fills you with joy and bliss.

Reference to this has been around for several thousand years in the Hindu tradition. The wise men of the east followed their intuition or spiritual guidance to find Christ. The Star of the East is a synonym for the Christ energy point, something we all have access to within ourselves. Cam, Congleton, UK

More likely the "star" was an invention of second century Christians to make their myths more closely follow Old Testament prophecies. Paul Williams, London

Science cannot answer this. The star was not a naturally occurring heavenly body as the Bible clearly states that the star led the astrologers first to King Herod and then to Jesus, after Herod claimed he too wanted to worship the Christ.

A naturally occurring celestial body would not stop above a specific location to identify the whereabouts of Jesus. The star also put the life of Jesus in jeopardy by its first leading the Magi to Herod who wanted to kill the Messiah who he saw as a threat to his reign.

The result of this chain of events resulted in the murder of all male children in Bethlehem. Logically the origin of the "star" was evil and supernatural. If this was a naturally occurring event God would surely have foreseen it and would not have allowed the life of his son to be endangered by its presence. Chris, Nottingham, UK

The "great northern star" is the star Sirius that appears to follow the sun (Jesus) at that time of year if you live in that part of the world. The 12 disciples represent the 12 signs of the zodiac and the reference to fishes is a reference to the movement into Pisces which according to the calendar was when the story of Christ came about.

All religion is merely interpretation of astrological events. So the story of Christ did happen but only when you realise it was just the stars. No real man ever existed all historical evidence of the time proves this. Sam

Sam, this is slightly incorrect as there is a wealth of supporting evidence for an individual called Jesus being alive and active at this time. Whether the star was a supernova, conjunction of planets or early alien spaceship it is hard to tell. One must look at the source of the original "story" and decide whether it can be verified at all Jenny, Southampton

The great north star is not Sirius, but Polaris. Sirius is much brighter than Polaris and is often mistaken for the North Star, as people assume the North Star is the brightest. Which can be quite embarrassing if you're navigating by it as I don't think its ascension/declination ever approach that of Polaris. David, Highworth

If we start going down the route of "metaphysics" and metaphors (Sun = Jesus?) then why discuss the physical possibilities of the Star at all? You have to accept that there is some historical accuracy in the New Testament otherwise why enter into the debate?

I think the historical accuracy of the New Testament DOES stand up to scrutiny, otherwise all the atheists and other sceptics would have torn it apart by now, but they can't. So, what was the nature of the Star? Well, I think any one of the scientific explanations sounds good to me. John Baharie, Sunderland

I am a Shia Muslim. I believer Jesus was born on 25th day of 11th month of the lunar calendar. We celebrated his birth last month. I think when you calculate it back, you get the date of Jesus' birth accurately. As to the star, it was Angel Gabriel coming down to Earth. Ali, Manchester, UK

Story from BBC NEWS:http://news.bbc.co.uk/go/pr/fr/-/2/hi/uk_news/magazine/7791571.stm